Controlling mechanism for hydraulic presses and the like.



W. R. CLARK. CONTROLLING MECHANISM FOR HYDRAULIC PRESSES A APPLICATION FILED JUNE 7 1912. 1,1 03,035.

ND THE LIKE.

Patented July 14, 1914.

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W. R. CLARK.

CONTROLLING MECHANISM FOR HYDRAULIC PRESSES APPLICATION FILED JUNE 7, 1912. 1 9 1 3,935 D AND THE LIKE.

Patented July 14, 1914.

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WALTER R. CLARK, OF BRIDGEPORT, CONNECTICUT, ASSIG-NOR TO 'BRIDGEPORT BRASS COMPANY, OF BRIDGEPOB-T, CONNECTICUT, A CORPORATION OF CONNECTICUT.

CONTROLLING MECHANISM FOR HYDRAULIC TRESSES AND THE LIKE.

Patent-ed July Mt, ilgtd. Serial No. 702,273.

ll,ll.@3,? 5. Specification of Letters Patent.

Application filed June 7, 1912.

source may be used during certain phases of the operation.

To these and other ends, the invention consists in the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawings, Figure 1 is a diagrammatic view of a controlling mechanism embodying my invention, showing the parts in the position which they oc- To all whom it may concern:

Be it known that I, WALTER R. CLARK, a citizen of the United States, residing in Bridgeport, county of Fairfield, and State of Connecticut, have invented certain new and useful Improvements in Controlling Mechanism for Hydraulic Presses and the like, of which the following is a full, clear, and exact description.

This invention relates mechanism for hydraulic presses, draw benches, and other machinery operated by fluid pressure, and it refers especially to controlling mechanism for machines in which a ram or other moving part is arranged for operation by fluid under high pressure or fluid from a source of low pressure, or fluid from both high and low pressure sources. Usually, the reciprocating rain or other member ordinarily employed for acting on the work is actuated by low pressure until the tool meets the work, and then water under high pressure is permitted to act on the ram in order to perform the working stroke, the return stroke being effected under low pressure. Ordinarily the low pressure water acts much more quickly than the high pressure water, so that con siderable time is saved by having the lowpressure water produce the return stroke of the ram or other member and the idle ortion of the operative stroke e. that por tion of the operative stroke which precedes the meeting of the tool with the work.

The object of the invention is to provide a simple. efficient system for illltOlDiltlCflll) changing over from high to low pressure and vice versa in order to meet the above conditions. I contemplate especially the use in connection with the fluid operated prime mover and the high and low pressure mains or pipes. of simple valve mechanism controlling the respective pressure mains and actuated effectively and directly by means called into action automatically by changes in the velocity of the fluid entering or leaving the prime mover. Under normal condi tions the low pressure water will have ac cess to the prime mover, but as the tool. meets the work the valve mechanism is instantly actuated in an automatic manner to cut off low pressure water from the prime mover and admit high pressure water to the latter, although in some cases water from both a high pressure source and a low pressure to controlling tool of the hydraulic press or the like has met the work, Fig. 3 is a diagram of a modified form of apparatus, showing the parts in a position corresponding to Fi 1. Fig. .4 is a similar view of said modified form of device, showing responding to Fig. 2, and Figs. 5 and 6 are diagrammatic sections of a further form of the motor device for actuatin the valve in the high pressure main, sai valve being shown closed in Fig. 5 and open in Fig. 6.

Referring to the drawings and particularly to Figs. 1 and 2, A denotes generally the prime mover for operating the ram or other part of the hydraulic press or other machine. This prime mover is conveniently ing a reciprocating piston 11. A four-way valve B is adapted to establish communication between the inlet pipe or passage 12. connected with the high pressure main C and the low pressure main D, and a port 12 at cue end of the cylinder 10; and said four-way valve also establishes communication between a port 13 at the opposite end of the cylinder 10 and an exhaust pipe or passage 1* communicating with a motor de vice E for controlling a valve C in the high pressure line. \Vhen the piston 11 has completed its stroke in one direction it may be the four-way valve B into position to establish communication between the port 12 and the exhaust pipe 14, and connnunication between the port 13 and the pressure main 12. Connection between the "four-way valve B and the port 12 is effected by means of a pipe or passage 15. and in a similar manner the port 13 is connected with the four-way valve by means of a pipe or passage 16. 1 The motor device E cupy when the piston of the prime mover is I at the beginning of its operative stroke,

it in a position correversed in an obvious manner by turning Fig. 2 is asimilar view showing the parts in the position which they occupy when the illustrated as comprising a cylinder 10 havis shown as compri ing a casing or Cylinder 17 containing a reciprocating piston 18. The exhaust fluid enters the casing 17 at 19 and leaves said casing through a port 20. The piston 18 is provided with a piston rod 21 sliding through one end of the Casing 17, and the body of the piston slides over a wall or partition 22 extending longitudinally of the easing and provided with end ports 23, 24, respectively and an intermediate port 25. When the parts are in the position shown in Fig. 1 theexhaust water flows through the space at the right hand side of the piston 18 and through the orts 24 and 25 into a chamber 26 beneath the partition or wall 22, and from said chamber 26 a portion of the liquid may flow hand side of the piston, although the greater part of the liquid passes directly out of the casing by way of the port 20. An enlarged portion or hub 27 on the piston rod 21 acts as a stop to prevent the piston from covering the ort 24, and a collar 28 on the piston red at the outside of the casing acts as a stop to prevent the piston from covering the port 23. Between the piston 18 of the motor device E and the valve C of the high pressure main C a suitable transmitting device is interposed. In the embodiment shown, it is aimed to reduce the movement of the high pressure valve as compared to that of the motor piston, and to this end the transmitting device is of the reducing type. Such device may conveniently comprise a link 29 pivoted to the casing 17 and connected by means of a link 30 with the extremity of the piston rod 21, the rod 31 carrying the valve 0 being pivoted to the link 30 intermediate of the connection with said link of the piston rod and link 29 respectively. ,It will be understood, however, that a reducing transmission device is not necessary in all cases and that if such a device is desirable, there is no restriction to any particular form of the same. As reviously intimated, the pipe or passage 12 orms a common inlet pipe to the prime mover into which both the high pressure and the low pressure mains discharge. A suitable valve F is provided in the low pressure main D in order to cut off the supply of low pressure water, and in the embodiment illustrated, this valve F is a spring actuated check'valve, although it is to be understood that said valve may be operated positively by suitable means if desired. 1

The operation of the apparatus is substantially as follows: Assuming the parts to be 1n the position shown in Fig. 1, with the piston 11 of the prime mover A at the beginning of its operative stroke, it will be understood that the pressure of the water which exhausts from the cylinder 10 by way of the port 13 as the operative stroke commences, is sufiicient to act on the motor piston 18 into the space at the leftwith considerable force in passing through the chamber at the right hand side of the motor piston. This holds the motor piston in substantially the position shown in Fig.

1. with each'of the ports 23, 24 and 25 completely uncovered, the pressure on the right hand side of the piston 18 being suflicient to overcome the comparatively low pressure at the left hand side of the piston (the outlet to the exhaust being comparatively free through the port 20), and to overcomein addition the pressure of the high pressure water on the valve C, which would tend to open said valve. In other words, the motor piston holds the high pressure valve closed, and with the high pressure main cut ofl from the prime mover the valve F in the low pressure line will be opened by the low pressure water against the action of its spring so that the piston of the prime mover will move forward quickly under the impulse of the low pressure water flowing into the cylinder 10 through the pipes 12 and 15. The tool of the hydraulic press or other machine usually meets the work when the piston 11 is intermediate of the endsof its stroke, and when this occurs the movement of said pis- I ton will be considerably retarded' Consequently the velocity of the water exhausting through the pipes 16 and 14 will be correspondingly decreased thereby cuttingdown the velocity of the water passing through the chamber at the right hand of the motor piston 18. Itwill be understood that when the exhaust water flows through this ehamher with considerable velocity there is a considerable pressure drop between the chamber at the right hand side of the piston and the chamber 26. In othei i'ords, the ports 24 and 25 throttle down themstinq fluid to a arge extent.

I The friction producefl h these ports or orifices varies as the squar e\ of the velocity of the fluid passing through t em, in accordance with a well known physical law, and hence as the velocity of the exhausting water is decreased by retarding of the piston 11, the friction produced by the ports 24'and 25, pressure drop between the chamber 26 and the chamber at the right of the motor piston, is reduced in greater proportion. The pressure 1n. the chamber 26 being now more nearly equal that in the chamber at the right of the piston, the pressure transmitted from the chamber 26 through the port 23 to the left hand side of the piston proportionately increases thereby disturbing the equilibrium of the partially balanced piston and thrusting the same to the right, as shown in Fig. 2. This causes the opening of the high pressure valve C and the high pressure water rushes past said valve and a part of it passes back to and closes the check valve F of the low pressure line, while the remainder of the high pressure water rushes through the comivalve F.

mon inlet pipes 12 and 15 into the cylinder 10 to commence and complete the actual working stroke of the prime mover piston at a high pressure but preferably at a much reduced speed.

The number and arrangement of the ports in the interior wall .or partition of the motor casing 17 may be varied as called for by circumstances. For example, the port may be entirely omitted, although in the arrangement shown this port acts to prevent the high pressure valve from being actuated too suddenly. In being thrust to the right (Fig. 2) the motor piston 18 covers the port 25 and, of course, this tends to increase the pressure drop between the chamber 26 and the chamber at the right of the piston thereby decreasing toa certain extent the sudden pushing force exerted at the left of the piston. By appropriate designing of the several parts it will be possible, of course, to actuate the piston prime mover at times by water derived in part from the high pressure source and in part from the low pressure source.

In the form of the apparatus shown in Figs. 8 and 4 the motor device for actuating the high pressure valve is arranged in the low pressure inlet instead of in the exhaust conduit. Likewise, the motor device is of somewhat modified form, comprising an elongated casing G having at one end a pressure chamber 32 interposed in the low pressure inlet pipe D back of the check At the opposite end of the easing G is a chambered portion 34 in which is located a cylindrical valve 35 carried directly by the piston rod 21 of the piston 18 in the chamber 32. The valve 35 coaets with a seat 36 in such a manner as to establish or cut off communication between the high pressure main C entering the chamber 34 at one side, and a branch 37 connecting the opposite side of, the casing 34 with the inlet pipe 12 for both high pressure water and low pressure water. In other words, the branch 37 communicates with the junction of the low pressure pipe D and the pipe 12 The chamber 32 is provided with a partition 22 similar to that described in connection with Figs. 1 and 2, and this partition is provided with ports 23, 24 and 25 similar to those previously described. The high pressure valve 35 is made in the form of a cylindrical piston against which the high pressure water entering the casing 34 acts in one direction. The high pressure water acts in the opposite direction on a smaller cylindrical piston 38 on the piston rod 21. Moreover, a spring 39 acts on the end of the piston rod and normally urges it toward the position .shown in Fig. 4. The areas of the piston 18 and of the pistons 35 and 38 are so chosen, and the other parts of the apparatus are so designed, that when low pres- &

sure water is flowing into the main cylinder 10 the piston 18 will be balanced in the position shown, allowing a free egress of low ressure water through the ports 23 and 25. When the piston 11 is retarded by the meeting of the tool with the work the velocity of the low pressure water entering through the pipe G and pipe 12 will be correspondingly decreased and the friction of the water passing through the ports or orifices 23 and 25 will be decreased in a greater proportion, thus increasing proportionately the pressure in the space beneath the partition and in the space at the right of the piston in accordance with the principles above described. Thus the equilibrium of the piston 18 will be disturbed, and it will be moved to the left as the combined pressures on its right hand side and on the right hand end of the high pressure piston valve 35 rise above the combined pressures on the left hand side of the piston and on the left hand side of the compensating piston 38.

In this manner the piston valve 35 will be moved to the left, thereby establishing com munication between the high pressure conduit C and the inlet pipe 12 A. portion of the high pressure water entering said inlet pipe passes back in the low pressure pipe D to close the low pressure valve F, while the remainder of such high pressure water will pass into the main cylinder 10 and thereby act during the working stroke of the machine.

In Figs. 5 and 6, I have shown a further modification of the device for actuating the high pressure valve. In this case, the easing of the device is provided at one end with a chamber 40 in which operates a "piston 41 having ports 42 which are always open. The spaces at opposite sides of the piston are connected with inlet and outlet branches respectively of the low pressure main D At the opposite end of the motor device is a chamber 43 into which high pressure water enters from the pipe C. The chamber43 has a valve seat 44 controlled by an ordinary valve 45 carried by the piston rod 41 of the piston 41. The side wall of the chamber 40 is of generally conical shape and is provided with longitudinal guides 46 in which the piston 41 is guided, the construction being such that when the piston is in the position shown in Fig. 5, open by-passes 47 are created at the edge of the piston permitting a considerable flow of water around the latter, whereas when the piston is moved to the left to the limit of its movement as shown in Fig. 6, said icy-passes are completely cut off and there is only a restricted flow of fluid past the piston by way of the perforations or ports 42. Fig. 5 shows the position of the parts under normal conditions, with a free flow of low pressure water through and past the piston. As the piston of the prime mover is retarded the velocity of the low pressure water entering the chamber 40 will be decreased, and the pressure at the right hand side of the piston 41 will be more nearly equalized with the pressure at the left hand side of said piston in accordance with the principles herein-be ore explained, thereby causing the piston 41 to be moved toward the left to open the high pressure valve 4-5 as shownin Fig. 6.

It will be understood," of course, that in all of the modifications described reversal of the prime mover is effected by means of a fourway valve B or similar device. In case the return stroke of the prime mover piston or other part is an entirely idle one, such stroke will obviously be effected under low pressure, and therefore with considerable quickness, whereas if the return stroke is used as a working stroke the high pressure water will be cut in and the low pressure water out off as soon as the moving part of the prime mover meets with a predetermined amount of resistance.

In case the prime mover of the hydraulic machine consists of a cylinder and piston,

as illustrated, andthe return stroke is an idle stroke, the high pressure water should preferably be connected to the rod side of the cylinder, and a large rod should be employed so that on the return stroke the low pressure on the full piston area will readily overcome the pressure on the smaller area at the opposite side of the piston. This quickens the return considerably. It is not absolutely necessary, however, that constant low pressure be on the full piston area, because if desired, a counter-weight or other device may be used to over balance the effect of the piston rod. The water exhausted from the prime mover can in this case pass to the low pressure tank or other source of low pressure water, but, of course, this is not essential.

As previously stated, I do not wish to limit myself to any specific form of prime mover nor, in the broad aspects of the invention, to any specific form of device for operating the high pressure valve, provided, such device is operated under the general principles herein explained. Moreover, I do not wish to limit myself to the use of az check valve for cutting off the low pressure water, as various changes in this and other respects may be made without departing from the scope of my invention as defined in the claims.

What I claim is: k

1. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure water, a source of low pressure water, means connecting said sources with said prime mover, and means actuated by a decrease in velocity of the liquid in the system, due to an increase in inlet connection an the cylinder the resistance encountered by the prime mover, to out 01f the .low pressure source from said prime mover and cut in the high pressure source; substantially as described.

2. The combination with a prime mover operated by liquid ressure and having an an exhaust connection, of a pressure main in communication with said inlet connection, a valve in said main, and a valve operating device actuated by the pressure of liquid in the system to normally hold said valve closed but operated to open said valve by a drop in the velocity of the liquid flowing in the system; substantially as described.

3. The combination with a prime mover' for a hydraulic press or the like, comprising a cylinder with oppositely located orts and a piston to reciprocate in said cy inder, of high and low pressure mains respectively, a connection between said mains and said cylinder whereby they are placed in communication with either of said orts to actuate the piston in either directlon, and means actuated by a decrease of velocity of the liquid in the system, due to the retarding of the piston, to establish communication of with the high pressure main and to cut off the cylinder from the low pressure main; substantially as described.

4. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure fluid to operate said prime mover, a second source of fluid pres sure, of less degree than the first but likewise capable of operating said prime mover, means connecting said sources with said prime mover, and means actuated by a decrease in the velocity of the fluid flowing through the system, due to an increase in the resistance encountered by the prime mover, to cut off the low pressure source from said prime mover and cut in the high pressure source,.said last named means including a movable element having opposite surfaces acted on by different portions of a stream of fluid involved in the operation of said prime mover; scribed.

5. In controlling mechanism for hydraulic presses and the like, a prime mover, a low pressure source normally connected with said prime mover to operate the same, a

igh pressure source, and means actuated by a change in velocity of the flow of fluid in the system to'cut out the low pressure source and cut in the high pressure source; substantially as described.

6. In co-ntrollin mechanism for hydraulic presses and the li e, a prime mover a normally open conduit connected therewith to supply said primev mover with motive fluid under low pressure, a normally closed conduit connected with said prime mover and with a source of motive fluid under high substantially as derespective sources, movable element pressure, and means actuated by the decrease of the pressure drop between opposite sides of an orifice through which the fluid flows at one point in the system, to cut off the low pressure source from the prime mover and cut in the high pressure source: substantially as described.

7. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure fluid to operate said pr me mover, a second source of pressure fluid of less degree than the first but likewise capable of operating said prime mover, means connecting said sources with sai prime mover to drive the latter in either direction by pressure from either of said sources, and means actuated by a decrease In the velocity of the fluid flowing through the system due to an increase in the resistance encountered by the prime mover, to cut oft the low pressure source from said prime mover and cut in the high pressure source; substantially as described.

8. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure fluid to operate said prime mover, a source of low pressure fluid to operate said prime mover, means connecting said low pressure source with said prime mover to drive the latter in either direction, and means actuated by the decrease of the pressure drop between opposite sides of an orifice through which the fluid flows at one point in the system, to cut ofl communication of the low pressure source with the prime mover and cut in the high pressure source; substantially as described.

9. The combination with the prime mover out a hydraulic press or other machine, of a source of high pressure fluid to operate said prime mover, a second source of pressure fluid of less degree than the first but likewise capable of operating said prime mover, means for connecting said sources with said prime mover, valves to control the flow of fluid to the prime moverirom the and means including a having opposite surfaces acted on by diflerent portions of a stream of fluid involved in the operation of said prime mover for actuating one of said valves; substantially as described.

10. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure fluid, a source of low pressure fluid, the pressure of each of said sources being sufliciently high to operate said prime mover independently of the other source, means to connect sai sources with said prime mover, and means actuated by. a change in velocity of the fluid flowing in the system, due to a change in the resistance encountered by the prime mover, to cut ofl one of said sources from said prime mover, and establish communication between the prime mover and the other source; substantially as described.

11. The combination with the prime mover of a hydraulic press or other machine, of a high pressure conduit, a low pressure conduit, means to connect said conduits with said prime mover, and means actuated by a decrease in the velocity or the fluid flowing through the system due to an increase in the resistance encountered by the prime mover to open the high pressure valve, said last named means including a movable element having opposite surfaces subjected to the pressures of diflerent portions of a stream of fluid involved in the operation of said prime mover; substantially as described.

12. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure fluid, to operate said prime mover, a source of low pressure fluid to operate said prime mover, means connecting said sources with said prime mover, a valve controlling communication of the prime mover with the high pressure source, and means for opening said valve by a decrease of velocity of the fluid flowing through the system due to an increase in the resistance encountered by the prime mover, including a movable element having opposite surfaces acted on by the pressures of diflerent portions of a stream of fluid involved in the low pressure operation of said prime mover; substantially as described.

13. lin controlling mechanism for hydraulic presses and the like, a prime mover for the press or other machine, a high pressure conduit, a low pressure conduit, the pressure in each of said conduits being suiticicntly high to operate said prime mover independently of the pressure in the other conduit, means for connecting said conduits with said prime mover, valve mechanism to control said conduits, and a motor device for the said valve mechanism, actuated by a change in velocity of the fluid flowing in the system, due to an opposite change in the resistance encountered by the prime mover; substantially as described.

14:. In controlling mechanism for hydraulic presses and the like, a prime mover for the press or other machine, a source of high pressure fluid to operate said prime mover, a source of pressure fluid of less degree than the first but capable of actuating said prime mover independently of said first source. means r'or connecting said sources with said prime mover, and controlling means for one of said sources, including a movable element ='having opposite surfaces subjected respectively to the pressures of difi'erent ortions of a stream of fluid involved in the operation of the prime mover by pressure from the other fluid source; substantially as described.

15. The combination with the prime mover of a hydraulic press or other machine, of a source ofhigh pressure fluid to operate said prime mover, a second source of pressure fluid of less degree than the first, but likewise capable of operating said prime ,mover, means for connecting said sources with said prime mover, valve mechanism to control the flow of fluid to the prime mover from the respective sources, and means for operating said valve mechanism, to cut one of said sources and cut in the other source, by a change in velocity of the fluid flowing in the system, due to an inverse change in the resistance encountered by the prime mover; substantially as described.

16. In controlling mechanism for hydraulic presses and the like, a prime mover for the press or other machine, a high pressure conduit, a low pressure conduit, means for connecting said conduits with said prime mover, valves in the respective conduits, and an operating device for the high pressure valve including a movable element having opposite surfaces acted on respectively by the pressures of difi'erent portions of a stream of fluid involved in the low pressure operation of the prime mover; substantially as described.

17 In controlling mechanism for hydraulic presses and the like, a prime mover for the press or other machine, a high pressure conduit, a low pressure conduit, means for connecting said conduits with said prime mover, valves in the respective conduits, an operating device for the high pressure valve, including a movable element having opposite surfaces acted on respectively by the pressures of different portions of a stream of fluid involved in the low pressure operation of the prime mover, and means presenting a restricted orifice separating said stream of fluid into such different portions; substantially as described.

18. In controlling mechanism for hydraulic presses and the like, a prime mover for the press or other machine, a high pressure conduit, a low pressure conduit, means for connecting said conduits with said prime mover, valves for controlling the respective conduits, and means actuated by a decrease in the velocity of the fluid flowing through the system to open the valve of one-of said conduits, said last named means including a movable element having opposite surfaces subjected respectively to t difi'erent portions of a stream of fluid involved in the operation of the prime mover bv liquid derived from the other conduit; substantially as described.

19. In control-ling mechanism for hydraulic presses and the like, a prime mover, a

e pressures of common inlet conduit connected therewith for supp-lying fluid under high or low pressures respectively, high and low pressure conduits connected with said common inlet conduit, an exhaust conduit, a controlling valve for the high pressure conduit, and a motor device for operating said valve actuated by changes of velocity of the fluid passing through the exhaust conduit; substantially as described.

20. The combination With the prime mover of a hydraulic press or the like, of a pressure main connected with said prime mover, a valve in said main, a casing through which the liquid flows at a velocity determined by the resistance encountered by the prime mover, a partition extending lengthwise of said casing and creating a piston chamber therein and having one or more restricted orifices, and a piston in said piston chamber connected with said valve; substantially as described.

21-. In controlling mechanism for hydraulic presses and the like, the combination of a prime mover, a conduit connected therewith, a valve in said conduit, a motor device for said valve actuated by changes of velocity in the liquid flowing through the system, and means to convert comparatively large movements of said motor device into smaller 95 movements of said valve; substantially as described. 4 i

'22. In controlling mechanism for hydraulic presses and the like, the combination of a prime mover, a supply conduit connected therewith, an exhaustconduit connected therewith a valve in the supply conduit, and a motor device in the exhaust conduit operatively connected with said valve; substantially as described.

23. In controlling mechanism for hydraulic presses and the like, the combination of a prime mover, a supply conduit connected therewith, an exhaust conduit connected therewith, a valve in one of said conduits, and a motor device for said valve located in the other conduit; substantially as described.

24. In controlling mechanism for hydraulic presses and the like, the combination of a prime mover, a supply conduit connected therewith, an exhaust conduit connected therewith, a valve in one of said conduits, a motor device in the other conduit, and means for converting comparatively large move- 2 ments of said motor device into smaller movements of said valve; substantially as described.

25. In controlling mechanism for hydraul1c presses and the like, the combination of a prime mover, a supply conduit" connected therewith, an exhaust conduit connected therewith, a valve in one of said conduits, a motor device in the other conduit, and a reducing device ing said motor device With said valve; substantially as described.

26. The combination with the prime mover of a hydraulic press or other machine, of a source of high pressure liquid to operate said prime mover, a second source of pressure liquid of less degree than the first, but likewise capable of operating said prime mover, means for connecting sai sources With said prime mover, valve mechanism to control the flow of liquid to the rime mover from the respective sources, and automatic means for actuating said valve mechanism, to cut out the low pressure source and cut in the high pressure source, by a decrease in the velocity of the liquid flowing in the system, due to an increase in the resistance encountered by the prime mover; substantially as described.

In Witness whereof, I have hereunto set my hand on the 5 day of June, 1912.

WALTER a. CLARK,

Witnesses:

JOSEPH B. HARRIS, RONALD C. HANDS. 

